Field of the Invention
The present invention relates to an olefin-polymerizing catalyst capable of forming in one polymerization system two homopolyolefins, each of said homopolyolefins being an isotactic polyolefin in which the disorder of monomer units alignment is in respective specified range. The present invention further relates to a process for producing an olefin polymer using said catalyst and a polypropylene produced by said process which is useful for production of a biaxially oriented film. More particularly, the present invention relates to a process for producing an olefin polymer excellent in stiffness and stretchability and successfully usable for formation of films, fibers, blow-molded articles, extrusion-molded articles, etc., an olefin-polymerizing catalyst used for production of such a polymer, a polypropylene for use in the production of a biaxially oriented film which can give a biaxially oriented film excellent in transparency and stiffness while retaining a particularly excellent stretchability, and a biaxially oriented film produced from said polypropylene.
Biaxially oriented films are extensively used as packaging materials because of their excellence in transparency, gloss, stiffness and water vapor barrier property. With the aim of improving the film properties, such as stiffness, of biaxially oriented film, highly crystalline homopolymers of propylene obtained with a high-stereospecificity catalyst have conventionally been used. However, such highly crystalline homopolymers of propylene have a fault that they are inferior in stretchability and apt to make troubles such as film breaking in the course of stretching. Thus, a variety of methods have so far been proposed for improving the stretchability of highly crystalline polypropylene. As one example of such proposals, copolymerization of propylene with a small amount of ethylene is known. Concretely speaking, JP-B-46-11027 has proposed a process for producing a polypropylene for use in production of films which comprises polymerizing propylene together with a very small amount of ethylene in the presence of a coordination catalyst and a hydrocarbon, hydrogen chloride or chlorinated hydrocarbon solvent so that one mole of the monomer unit in the resulting polymer becomes containing 0.01 mole or less of ethylene unit. Further, in JP-B-64-6211, there is proposed a process for producing a polypropylene improved in stretchability which comprises feeding propylene together with a small amount of ethylene into polymerization system using a catalyst consisting of an organoaluminum compound and titanium trichloride prepared by reducing titanium tetrachloride with an organoaluminum compound and further activating the reduced product by a treatment using a complex-forming agent, a treatment using an organoaluminum compound, a treatment using titanium tetrachloride or a combination thereof so that the resulting polymer comes to have an ethylene content of 0.1-1.0% by weight. Further, in JP-B-3-4371, there is proposed a process for producing a biaxially oriented polypropylene film excellent in transparency, stiffness and impact resistance by using a polypropylene of which ethylene content is 0.1-2% by mole and isotacticity is in a specified range. Any of these processes, however, have been unsatisfactory as a method for obtaining a polypropylene for a biaxially oriented film simultaneously having an excellent transparency and a high stiffness while retaining a good stretchability.
The object of the present invention is to provide an olefin-polymerizing catalyst capable of forming in one polymerization system two homopoly-olefins, each of said homopolyolefins being an isotactic polyolefin in which stereoirregularity of monomer units is in respective specified range, a process for producing an olefin polymer using said catalyst, and a propylene for use in the production of a biaxially oriented film excellent in stretchability and having high transparency and stiffness.
In view of the above-mentioned state of things, the present inventors have conducted extensive studies to find that a polyolefin in which the stereoirregularity is in a specified range can be obtained by using a specified catalyst system, and that a biaxially oriented film simultaneously having high transparency and stiffness while retaining an excellent stretchability can be obtained from a polypropylene obtained by the use of said catalyst system which has a cold decalin-soluble fraction (23xc2x0 C. decalin-soluble fraction) content falling in a specified range, shows a specified complex elastic molulus in a specified temperature range, and has a melt flow rate (referred to as MFR, too) falling in a specified range. Based on this finding, the present invention has been accomplished.
Thus, the present invention relates to a process for producing an olefin polymer which comprises homo- or co-polymerizing an olefin by the use of a olefin-polymerizing catalyst consisting of:
(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,
(B) an organoaluminum compound, and
(C) at least two electron donative compounds including electron donative compound (xcex1) and electron donative compound (xcex2), provided that 105xc2x0 C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out a polymerization using the electron donative compound (xcex1) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index (mmrr/mmmm) satisfying the following formula:
0xe2x89xa6mmrr/mmmmxe2x89xa60.0068
and 105xc2x0 C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out a polymerization using the electron donative compound (xcex2) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index satisfying the following formula:
0.0068xe2x89xa6mmrr/mmmmxe2x89xa60.0320;
an olefin-polymerizing catalyst consisting of:
(A) a solid catalyst component containing magnesium, titanium, halogen and an electron donative compound as essential components,
(B) an organoaluminum compound, and
(C) at least two electron donative compounds including electron donative compound (xcex1) and electron donative compound (xcex2), provided that 105xc2x0 C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out a polymerization using the electron donative compound (xcex1) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index (mmrr/mmmm) satisfying the following formula:
0xe2x89xa6mmrr/mmmmxe2x89xa60.0068
and 105xc2x0 C. xylene-insoluble fraction of a homopoly-propylene obtained by carrying out a polymerization using the electron donative compound (xcex2) together with the solid catalyst component and the organoaluminum compound shows a pentad stereoirregularity index satisfying the following formula:
0.0068xe2x89xa6mmrr/mmmmxe2x89xa60.0320;
and a polypropylene for use in the production of a biaxially oriented film obtained by carrying out a polymerization using said catalyst system, wherein:
(1) the content of 23xc2x0 C. decalin-soluble fraction of the polypropylene is in the range of from 3.0 to 10.0% by weight,
(2) when a vibration of 110 Hz is applied to the polypropylene, the polypropylene shows a complex elastic modulus of 1.0xc3x97109 dynes/cm2 at a temperature falling in the range of from 134xc2x0 C. to 152xc2x0 C., and
(3) melt flow rate (MFR) of the polypropylene at 230xc2x0 C. is in the range of from 0.5 to 10.0 g/10 minutes.
Further, the present invention relates also to a biaxially oriented film obtained by subjecting said polypropylene for use in the production of biaxially oriented film to a stretching processing.
Next, the present invention is explained below in more detail.
The catalyst system used for production of the polyolefin of the present invention consists of (A) a solid catalyst component containing magnesium, titanium, halogen and electron donative component as essential components, (B) an organoaluminum compound and (C) an electron donative component.
(a) Solid Catalyst Component (A)
As the solid catalyst component (A) of the present invention containing magnesium, titanium, halogen and an electron donative compound as essential components, those generally called titanium-magnesium complex catalysts can be used. Such solid catalyst component (A) can be obtained by contacting the following magnesium compound, titanium compound and electron donative compound mutually.
As the titanium compound used for the synthesis of solid catalyst component (A), for example, the titanium compounds represented by the following general formula:
xe2x80x83Ti(OR1)aX4xe2x88x92a
wherein R1 represents a hydrocarbon group having 1-20 carbon atoms, X represents a halogen atom, and a represents a number satisfying 0xe2x89xa6axe2x89xa64, can be referred to. More specifically, titanium tetrahalide compounds such as titanium tetrachloride, titanium tetrabromide, titanium tetraiodide and the like, alkoxytitanium trihalide compounds such as methoxytitanium trichloride, ethoxytitanium trichloride, butoxytitanium trichloride, phenoxytitanium trichloride, ethoxytitanium tribromide and the like, dialkoxytitanium dihalide compounds such as dimethoxytitanium dichloride, diethoxytitanium dichloride, dibutoxytitanium dichloride, diphenoxytitanium dichloride, diethoxytitanium dibromide and the like, trialkoxytitanium halide compounds such as trimethoxytitanium chloride, triethoxytitanium chloride, tributoxytitanium chloride, triphenoxytitanium chloride, triethoxytitanium bromide and the like, and tetraalkoxytitanium compounds such as tetramethoxytitanium, tetraethoxytitanium, tetrabutoxytitanium, tetraphenoxytitanium and the like can be referred to. These titanium compounds may be used either in the form of a single compound or in the form of a mixture of two or more compounds. Further, if desired, these titanium compounds may be used after dilution with a hydrocarbon or halogenated hydrocarbon compound or the like.
As the magnesium compound used in the synthesis of solid catalyst component (A), reductive magnesium compounds having a magnesium-carbon bond or a magnesium-hydrogen bond and non-reductive magnesium compounds can be used. Specific examples of the reductive magnesium compound include dimethylmagnesium, diethylmagnesium, dipropylmagnesium, dibutylmagnesium, dihexylmagnesium, butylethylmagnesium, ethylmagnesium chloride, butylmagnesium chloride, hexylmagnesium chloride, butylethoxymagnesium, butylmagnesium hydride and the like. If desired, these reductive magnesium compounds may be used in the form of a complex compound with an organoaluminum compound. On the other hand, specific examples of the non-reductive magnesium compounds include magnesium dihalide compounds such as magnesium dichloride, magnesium dibromide, magnesium diiodide and the like; alkoxymagnesium halide compounds such as methoxymagnesium chloride, ethoxymagnesium chloride, butoxymagnesium chloride, isopropoxymagnesium chloride, phenoxymagnesium chloride and the like; dialkoxymagnesium compounds such as diethoxymagnesium, dibutoxymagnesium, diisopropoxymagnesium, diphenoxymagnesium and the like; and magnesium carboxylates such as magnesium laurate, magnesium stearate and the like. If desired, said non-reductive magnesium compound may be a compound synthesized from a reductive magnesium compound according to a known method either previously or at the time of preparation of the solid catalyst component.
As the electron donative compound used in the synthesis of solid catalyst component (A), oxygen-containing electron donative compounds such as alcohols, phenols, ketones, aldehydes, carboxylic acids, esters of organic and inorganic acids, ethers, acid amides, acid anhydrides and the like; nitrogen-containing electron donative compounds such as ammonia, amines, nitriles, isocyanates and the like; etc. can be referred to. Of these electron donative compounds, esters of organic and inorganic acids and ethers are preferred.
As the ester of organic acid, esters of mono- and poly-carboxylic acids can be used preferably, of which examples include esters of aliphatic carboxylic acids, esters of olefinic carboxylic acids, esters of alicyclic carboxylic acids and esters of aromatic carboxylic acids. Specific examples thereof are methyl acetate, ethyl acetate, phenyl acetate, methyl propionate, ethyl propionate, ethyl butyrate, ethyl valerate, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl benzoate, butyl benzoate, methyl toluate, ethyl toluate, ethyl anisate, diethyl succinate, dibutyl succinate, diethyl malonate, dibutyl malonate, dimethyl maleate, dibutyl maleate, diethyl itaconate, dibutyl itaconate, monoethyl phthalate, dimethyl phthalate, methyl ethyl phthalate, diethyl phthalate, di-n-propyl phthalate, diisopropyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, di-n-octyl phthalate, diphenyl phthalate and the like.
As the esters of inorganic acid, the silicon compounds represented by the following general formula:
R2nSi(OR3)4xe2x88x92n
wherein R2 represents a hydrocarbon group having 1-20 carbon atoms or a hydrogen atom, R3 represents a hydrocarbon group having 1-20 carbon atoms, and n represents a number satisfying 0xe2x89xa6nxe2x89xa64, can be used preferably. Specific examples of said silicon compound include tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetraphenoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, t-butyltrimethoxysilane, isopropyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, dipropyldimethoxysilane, propylmethyldimethoxysilane, diisopropyldimethoxysilane, dibutyldimethoxysilane, diisobutyldimethoxysilane, di-t-butyldimethoxysilane, butylmethyldimethoxysilane, butylethyldimethoxysilane, t-butylmethyldimethoxysilane, hexylmethyldimethoxysilane, hexylethyldimethoxysilane, dodecylmethyldimethoxysilane, dicyclopentyldimethoxysilane, cyclopentylmethyldimethoxysilane, cyclopentylethyldimethoxysilane, cyclopentylisopropyldimethoxysilane, cyclopentylisobutyl-dimethoxysilane, cyclopentyl-t-butyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylethyldiethoxysilane, cyclohexylisopropyldimethoxy-silane, cyclohexylisobutyldimethoxysilane, cyclohexyl-t-butyldimethoxysilane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, vinylmethyldimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, isobutyltriethoxysilane, t-butyltriethoxysilane, isopropyltriethoxysilane, cyclohexyltriethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, dipropyldiethoxysilane, propylmethyldiethoxysilane, diisopropyldiethoxysilane, dibutyldiethoxysilane, diisobutyldiethoxysilane, di-t-butyldiethoxysilane, butylmethyldiethoxysilane, butylethyldiethoxysilane, t-butylmethyldiethoxysilane, hexylmethyldiethoxysilane, hexylethyldiethoxysilane, dodecylmethyldiethoxysilane, dicyclopentyldiethoxysilane, dicyclohexyldiethoxysilane, cyclohexylmethyldiethoxysilane, cyclohexylethyldiethoxysilane, diphenyldiethoxysilane, phenylmethyldiethoxysilane, vinylmethyldiethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, phenyltri-t-butoxysilane, 2-norbornanetrimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, trimethylphenoxysilane, methyltriallyloxysilane, and the like.
As the ethers, the dialkyl ether compounds such as those represented by the following general formula: 
wherein R4 to R7 each represents linear or branched alkyl group having 1-20 carbon atoms, alicyclic group, aryl group, alkylaryl group or arylalkyl group, provided that R4 to R7 may be identical with or different from one another and each of R4 and R5 may also be a hydrogen atom, can be referred to. Specific examples of the ether compound include diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diamyl ether, diisoamyl ether, dineopentyl ether, dihexyl ether, dioctyl ether, methyl butyl ether, methyl isoamyl ether, ethyl isobutyl ether, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2-isopropyl-2-3,7-dimethyloctyl-1,3-dimethoxypropane, 2,2-diisopropyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclohexylmethyl-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2-isopropyl-2-isobutyl-1,3-dimethoxypropane, 2,2-diisopropyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclohexyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2,2-dicyclopentyl-1,3-dimethoxypropane, 2-heptyl-2-pentyl-1,3-dimethoxypropane and the like.
Among these electron donative compounds, the ester compounds are particularly preferred.
As the method for producing such solid catalyst component, for example, the methods disclosed in JP-B-52-39431, JP-B-52-36786, JP-A-54-94590, JP-A-55-36203, JP-A-56-41206, JP-A-57-63310, JP-A-57-59916, JP-A-58-83006, JP-A-61-218606, JP-A-1-319508, JP-A-3-706, etc. can be referred to.
These methods can be exemplified by the following:
(1) a method of reacting a liquid magnesium compound or a complex compound consisting of a magnesium compound and an electron donative compound with a depositing agent and thereafter treating the reaction product with a titanium compound or a combination of titanium compound and electron donative compound;
(2) a method of treating a solid magnesium compound or a complex compound consisting of a solid magnesium compound and an electron donative compound with a titanium compound or a combination of titanium compound and electron donative compound;
(3) a method of reacting a liquid magnesium compound with a liquid titanium compound in the presence of an electron donative compound and thereby depositing a solid titanium composite compound;
(4) a method of further treating the reaction product obtained by (1), (2) or (3) with a titanium compound or a combination of electron donative compound and titanium compound;
(5) a method of reducing an alkoxytitanium compound with an organomagnesium compound such as Grignard reagent or the like in the presence of an organic silicon compound having a Sixe2x80x94O bond to obtain a solid product, followed by treating said solid product with an ester compound, an ether compound and titanium tetrachloride;
(6) a method of mutually contacting and reacting a metal oxide, dihydrocarbylmagnesium and a halogen-containing alcohol to obtain a product, followed by treating or not treating the product with a halogenating agent and then contacting the product with an electron donative compound and a titanium compound;
(7) a method of treating or not treating a magnesium compound such as a magnesium salt of organic acid, alkoxymagnesium or the like with a halogenating agent followed by contacting the magnesium compound with an electron donative compound and a titanium compound; and
(8) a method of treating the compound obtained in (1) to (7) with any one of halogen, halogen compound and aromatic hydrocarbon.
Among these methods for synthesizing a solid catalyst, the methods (1) to (5) are preferred, and the method (5) is particularly preferred.
Although such solid catalyst component (A) can be used in itself alone, it may also be used after impregnation into a porous material such as inorganic oxides, organic polymers and the like, if desired. As said porous inorganic oxide, SiO2, Al2O3, MgO, TiO2, ZrO2, SiO2xe2x80x94Al2O3 composite oxide, MgOxe2x80x94Al2O3 composite oxide, MgOxe2x80x94SiO2xe2x80x94Al2O3 composite oxide and the like can be referred to. As said porous organic polymer, polystyrene type, polyacrylic ester type, polyacrylonitrile type, polyvinyl chloride type, and polyolefin type of polymers can be referred to, of which specific examples include polystyrene, styrene-divinyl-benzene copolymer, styrene-n,nxe2x80x2-alkylenedimethacrylamide copolymer, styrene-ethylene glycol dimethyl methacrylate copolymer, polyethyl acrylate, methyl acrylate-divinyl-benzene copolymer, ethyl acrylate-divinylbenzene copolymer, polymethyl methacrylate, methyl methacrylatedivinylbenzene copolymer, polyethyleneglycol dimethyl methacrylate, polyacrylonitrile, acrylonitrile-divinyl-benzene copolymer, polyvinyl chloride, polyvinylpyrrolidine, polyvinylpyridine, ethylvinylbenzenedivinylbenzene copolymer, polyethylene, ethylene-methyl acrylate copolymer, polypropylene and the like.
Of these porous materials, SiO2, Al2O3 and styrene-divinylbenzene copolymer are preferred.
(b) Organoaluminum Compound (B)
The organoaluminum compounds which can be used as component (B) of the present invention are those having at least one Al-carbon bond in one molecule.
Typical organoaluminum compounds of the present invention are represented by the following general formulas:
R8mAlY3xe2x88x92m
R9R10Alxe2x80x94Oxe2x80x94AlR11R12
wherein R8 to R12 each represents a hydrocarbon group having 1-8 carbon atoms, provided that R8 to R12 may be identical with or different from one another, Y represents halogen, hydrogen or alkoxy group, and m represents a number satisfying 2xe2x89xa6mxe2x89xa63. Specific examples of such organoaluminum compound include trialkylaluminums such as triethylaluminum, triisobutylaluminum, trihexylaluminum and the like, dialkylaluminum hydrides such as diethylaluminum hydride, diisobutylaluminum hydride and the like, mixtures of a trialkylaluminum and a dialkylaluminum halide such as mixture of triethylaluminum and diethylaluminum chloride, and alkylalumoxanes such as tetraethyldialumoxane, tetrabutyldialumoxane and the like.
Of these organoaluminum compounds, preferred are trialkylaluminums, mixtures of a trialkylaluminum and a dialkylaluminum halide and alkylalumoxanes, and particularly preferred are triethylaluminum, triisobutylauminum, mixture of triethylaluminum and diethylaluminum chloride, and tetraethyldialumoxane.
(c) Electron Donative Compound (C)
As the electron donative compound (C) of the present invention, at least two electron donative compounds including electron donative compound (xcex1) and electron donative compound (xcex2) are used, wherein said electron donative compounds (xcex1) and (xcex2) satisfy the following conditions. Thus, 105xc2x0 C. xylene-insoluble fraction of a homopolypropylene obtained by carrying out polymerization using electron donative compound (xcex1) together with the above-mentioned solid catalyst component (A) and organoaluminum compound (B) shows a pentad stereoirregularity index (mmrr/mmmm) satisfying the following condition:
0xe2x89xa6mmrr/mmmmxe2x89xa60.0068,
preferably the following condition:
0.0004xe2x89xa6mmrr/mmmmxe2x89xa60.0068,
and further preferably the following condition:
0.0004xe2x89xa6mmrr/mmmmxe2x89xa60.0060,
and 105xc2x0 C. xylene-insoluble fraction of a homopoly-propylene obtained by carrying out polymerization using electron donative compound (xcex2) together with the above-mentioned solid catalyst component (A) and organo-aluminum compound (B) shows a pentad stereoirregularity index satisfying the following condition:
0.0068xe2x89xa6mmrr/mmmmxe2x89xa60.0320,
preferably the following condition:
0.0068xe2x89xa6mmrr/mmmmxe2x89xa60.0200,
and further preferably the following condition:
0.0072xe2x89xa6mmrr/mmmmxe2x89xa60.0140.
As used in the present invention, the term xe2x80x9c105xc2x0 C. xylene-insoluble fractionxe2x80x9d means the weight (%) of a fraction measured according to the method of Kakugo et al. [Macromolecules, 21, 314-319 (1988)], namely by dissolving a polypropylene in xylene at 130xc2x0 C., throwing sea sand into the resulting solution, cooling the mixture to 20xc2x0 C., again heating the mixture, and measuring the weight (%) of a fraction which is not extracted at 105xc2x0 C. and extracted in the temperature range exceeding 105xc2x0 C. and not exceeding 130xc2x0 C. On the other hand, the term xe2x80x9cpentad stereoirregularity indexxe2x80x9d means peak intensity ratio of the pentad fraction mmrr (the peak appears at about 21.01 ppm when TMS standard is used) to the pentad fraction mmmm (the peak appears at about 21.78 ppm when TMS standard is used) in the pentamer unit of a polypropylene molecular chain as measured at 135xc2x0 C., at 270 MHz, on a solution of polymer in o-dichlorobenzene containing 10% by weight of C6D6 (concentration of polymer=150 mg/3 ml) by means of 13C-NMR (EX-270, manufactured by Nippon Denshi K. K.) according to the paper of A. Zambelli et al. [Macromolecules, 13, 687-689 (1975)].
In the present invention, as the electron donative compound used for preparation of electron donative catalyst component (C), the same electron donative compounds as used in the preparation of solid catalyst component (A) can be used. Preferably, electron donative compound (xcex1) and electron donative compound (xcex2) are independently selected from the organic silicon compounds mentioned below.
As such organic silicon compounds, those represented by the following general formula:
R2nSi(OR3)4xe2x88x92n
wherein R2 represents a hydrocarbon group having 1-20 carbon atoms or a hydrogen atom, R3 represents a hydrocarbon group having 1-20 carbon atoms, and n represents a number satisfying 0xe2x89xa6nxe2x89xa64, can be referred to. Specific examples of such organic silicon compound include the following:
tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetraphenoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, butyltrimethyoxysilane, isobutyltrimethoxysilane, t-butyltrimethoxysilane, isopropyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, dipropyldimethoxysilane, propylmethyldimethoxysilane, diisopropyldimethoxysilane, dibutyldimethoxysilane, diisobutyldimethoxysilane, di-t-butyldimethoxysilane, butylmethyldimethoxysilane, butylethyldimethoxysilane, t-butylmethyldimethoxysilane, isobutylisopropyldimethoxysilane, t-butylisopropyldimethoxysilane, hexylmethyldimethoxysilane, hexylethyldimethoxysilane, dodecylmethyldimethoxysilane, dicyclopentyldimethoxysilane, cyclopentylmethyldimethoxysilane, cyclopentylethyldimethoxysilane, cyclopentylisopropyldimethoxysilane, cyclopentylisobutyl-dimethoxysilane, cyclopentyl-t-butyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane, cyclohexylisopropyldimethoxy-silane, cyclohexylisobutyldimethoxysilane, cyclohexyl-t-butyldimethoxysilane, cyclohexylcyclopentyldimethoxysilane, cyclohexylphenyldimethoxysilane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, phenylisopropyldimethoxysilane, phenylisobutyldimethoxysilane, phenyl-t-butyldimethoxysilane, phenylcyclopentyldimethoxysilane, vinylmethyldimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, isobutyltriethoxysilane, t-butyltriethoxysilane, isopropyltriethoxysilane, cyclohexyltriethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, dipropyldiethoxysilane, propylmethyldiethoxysilane, diisopropyldiethoxysilane, dibutyldiethoxysilane, diisobutyldiethoxysilane, di-t-butyldiethoxysilane, butylmethyldiethoxysilane, butylethyldiethoxysilane, t-butylmethyldiethoxysilane, hexylmethyldiethoxysilane, hexylethyldiethoxysilane, dodecylmethyldiethoxysilane, dicyclopentyldiethoxysilane, dicyclohexyldiethoxysilane, cyclohexylmethyldiethoxysilane, cyclohexylethyldiethoxysilane, diphenyldiethoxysilane, phenylmethyldiethoxysilane, vinylmethyldiethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, phenyltri-t-butoxysilane, 2-norbornanetrimethoxysilane, 2-norbornanetriethoxysilane, 2-norbornanemethyldimethoxysilane, trimethylphenoxysilane, methyltriallyloxysilane, and the like.
Among the organic silicon compounds mentioned above, those preferably usable as electron donative compound (xcex1) are, for example, organic silicon compounds represented by the following general formula:
R13R14Si(OR15)2.
In this general formula, R13 represents C3-C20 hydrocarbon group in which the carbon atom adjacent to Si is a secondary or tertiary carbon atom, and specific examples thereof include branched chain alkyl groups such as isopropyl, sec-butyl, t-butyl, t-amyl and the like, cycloalkyl groups such as cyclopentyl, cyclohexyl and the like, cycloalkenyl groups such as cyclopentenyl and the like, and aryl groups such as phenyl, tolyl and the like. In the general formula, R14 represents C1-C20 hydrocarbon group, of which specific examples include straight chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl and the like, branched chain alkyl groups such as isopropyl, sec-butyl, t-butyl, t-amyl and the like, cycloalkyl groups such as cyclopentyl, cyclohexyl and the like, cycloalkenyl groups such as cyclopentenyl and the like, and aryl groups such as phenyl, tolyl and the like. In the general formula, R15 represents C1-C20 hydrocarbon group, and preferably C1-C5 hydrocarbon group.
Specific examples of the organic silicon compound which can be used as such electron donative compound include the following:
diisopropyldimethoxysilane, diisobutyldimethoxysilane, di-t-butyldimethoxysilane, t-butylmethyldimethoxysilane, isobutylisopropyldimethoxysilane, t-butylisopropyl-dimethoxysilane, dicyclopentyldimethoxysilane, cyclopentyl-isopropyldimethoxysilane, cyclopentylisobutyldimethoxysilane, cyclopentyl-t-butyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane, cyclohexylisopropyldimethoxysilane, cyclohexylisobutyldimethoxysilane, cyclohexyl-t-butyldimethoxysilane, cyclohexylcyclopentyldimethoxysilane, cyclohexylphenyldimethoxysilane, diphenyldimethoxysilane, phenylmethyldimethoxysilane, phenylisopropyldimethoxysilane, phenylisobutyldimethoxysilane, phenyl-t-butyldimethoxysilane, phenylcyclopentyldimethoxysilane, diisopropyldiethoxysilane, diisobutyldiethoxysilane, di-t-butyldiethoxysilane, t-butylmethyldiethoxysilane, dicyclopentyldiethoxysilane, dicyclohexyldiethoxysilane, cyclohexylmethyldiethoxysilane, cyclohexylethyldiethoxysilane, diphenyldiethoxysilane, phenylmethyldiethoxysilane, 2-norbornanemethyldimethoxysilane and the like.
Among the organic silicon compounds mentioned above, those preferably usable as electron donative compound (xcex2) are, for example, organic silicon compounds represented by the following general formula:
R16R17Si(OR18)2
wherein R16 represents a C1-C20 hydrocarbon group and particularly preferably a straight chain alkyl group such as methyl, ethyl, propyl, butyl, pentyl and the like; R17 represents a C1-C5 hydrocarbon group and particularly a hydrocarbon group having one carbon atom; and R18 represents a C1-C20 hydrocarbon group and preferably a C1-C5 hydrocarbon group.
Specific examples of such organic silicon compound which can be used as electron donative compound (xcex2) include the following:
dimethyldimethoxysilane, ethylmethyldimethoxysilane, propylmethyldimethoxysilane, butylmethyldimethoxysilane, pentylmethyldimethoxysilane, hexylmethyldimethoxysilane, heptylmethyldimethoxysilane, octylmethyldimethoxysilane, dodecylmethyldimethoxysilane and the like.
In the process for producing a polyolefin of the present invention, the method for feeding the catalyst components to a polymerization reactor is not particularly limited, so far as the catalyst components are fed in a moisture-free state in an inert gas such as nitrogen gas, argon gas or the like.
According to the polymerization process of the present invention, an olefin is polymerized in the presence of a catalyst consisting of a solid catalyst component (A), an organoaluminum compound (B) and an electron donative component comprising at least two electron donative compounds including electron donative compound (xcex1) and electron donative compound (xcex2). In this polymerization reaction, there is no particular limitation except that mmrr/mmmm of a homopolypropylene obtained by carrying out the polymerization in the presence of a catalyst consisting of (A), (B) and a single component (xcex1) must satisfy the following condition:
xe2x80x830xe2x89xa6mmrr/mmmmxe2x89xa60.0068
and mmrr/mmmm of a homopolypropylene obtained by carrying out the polymerization in the presence of a catalyst consisting of (A), (B) and a single component (xcex2) must satisfy the following condition:
0.0068xe2x89xa6mmrr/mmmmxe2x89xa60.0320.
In the polymerization process of the present invention, an olefin is polymerized in the presence of the above-mentioned catalyst. If desired, a preliminary polymerization may be carried out before carrying out the main polymerization process. The preliminary polymerization is effected, for example, by feeding a small amount of olefin in the presence of solid catalyst component (A) and organoaluminum compound (B), and it is preferably carried out in the state of a slurry. As the solvent used for preparing the slurry, inert hydrocarbons such as propane, butane, isobutane, pentane, isopentane, hexane, heptane, octane, cyclohexane, benzene or toluene can be referred to. In preparing the slurry, a liquid olefin may be used, if desired, in place of a part or the whole of the inert hydrocarbon solvent.
In carrying out the preliminary polymerization, the amount of organoaluminum compound may be selected from such a wide range as from 0.5 to 700 moles per mole of titanium atom in the solid catalyst component. The amount of organoaluminum compound is preferably from 0.8 mole to 500 moles, and particularly preferably from 1 mole to 200 moles, both on the same basis as above.
The amount of olefin consumed in the preliminary polymerization is from 0.01 to 1,000 g, preferably from 0.05 to 500 g, and particularly preferably from 0.1 to 200 g, per gram of the solid catalyst component.
In carrying out the preliminary polymerization, the concentration of slurry is preferably from 1 to 500 g of solid catalyst component per liter of solvent, and particularly preferably from 3 to 300 g solid catalyst component per liter of solvent. The temperature of preliminary polymerization is preferably from xe2x88x9220xc2x0 C. to 100xc2x0 C., and particularly preferably from 0xc2x0 C. to 80xc2x0 C. In the process of the preliminary polymerization, the partial pressure of propylene in the gas phase is preferably from 0.01 to 20 kg/cm2 and particularly preferably from 0.1 to 10 kg/cm2, provided that this condition is not applicable to propylene which is in a liquid state at the pressure and temperature of preliminary polymerization. Although the period of time of the preliminary polymerization is not critical, it is usually from 2 minutes to 15 hours.
In carrying out the preliminary polymerization, the method for feeding solid catalyst component, organoaluminum compound and olefin may be any of a method of contacting a solid catalyst component with an organoaluminum compound and thereafter feeding olefin and a method of contacting a solid catalyst component with olefin and thereafter feeding an organoaluminum compound. The method for feeding olefin may be any of a method of portionwise feeding olefin while keeping the inner atmosphere of polymerization reactor at a prescribed pressure and a method of wholly feeding a prescribed quantity of olefin at the beginning. It is also possible to add a chain transfer agent such as hydrogen or the like in order to regulate molecular weight of the polymer formed.
In subjecting the solid catalyst component to a preliminary polymerization with a small amount of olefin in the presence of an organoaluminum compound, the preliminary polymerization may be carried out in the presence of an electron donative compound, if desired. The electron donative compound used for this purpose is a part or the whole of the above-mentioned electron donative catalyst component (C). Its amount is 0.01-400 moles, preferably 0.02-200 moles and particularly preferably 0.03-100 moles per mole of titanium atom present in the solid catalyst component, and is 0.003-5 moles, preferably 0.005-3 moles and particularly preferably 0.01-2 moles per mole of the organoaluminum compound.
In carrying out the preliminary polymerization, the method for feeding the electron donative compound is not particularly limited. Thus, an electron donative compound may be fed independently of an organoaluminum compound, or after a previous contact with an organoaluminum compound. The olefin used in the preliminary polymerization may be identical with or different from the olefin used in the main polymerization step which will be mentioned later.
After carrying out a preliminary polymerization in the above-mentioned manner or without carrying out the preliminary polymerization, a main polymerization of olefin can be effected in the presence of a polymerization catalyst consisting of the above-mentioned solid catalyst component (A), organoaluminum compound (B) and electron donative catalyst component (C).
The solid catalyst component, organoaluminum compound and electron donative catalyst component consisting of at least two electron donative compounds may be fed either independently of one another or after mutually contacting any two of them. Regarding the electron donative compounds (xcex1) and (xcex2) as the electron donative catalyst components, it is allowable to use both of them at the time of preliminary polymerization or it is also allowable to use one of them in the preliminary polymerization and to use the other in the main polymerization or it is also allowable to use both of them firstly in the main polymerization.
In the main polymerization, the amount of the organoaluminum compound may be selected from such a wide range as from 1 mole to 1,000 moles per mole of titanium atom in the solid catalyst component. Particularly preferably, however, the amount of the organoaluminum compound is in the range of from 5 to 600 moles on the same basis as above.
In the main polymerization, the total amount of the electron donative catalyst component (C) is from 0.1 to 2,000 moles, preferably from 0.3 to 1,000 moles and particularly preferably from 0.5 to 800 moles per mole of titanium atom present in the solid catalyst component. The total amount of electron donative component (C) is from 0.001 to 5 moles, preferably from 0.005 to 3 moles and particularly preferably from 0.01 to 1 mole per mole of the organoaluminum compound.
The main polymerization can be effected at a temperature ranging from xe2x88x9230xc2x0 C. to 300xc2x0 C. and preferably from 20xc2x0 C. to 180xc2x0 C. Although there is no limitation upon the polymerization pressure, a pressure of from ordinary pressure to 100 kg/cm2 and preferably from about 2 to about 50 kg/cm2 is usually adopted from the viewpoint of industrial and economical practicabilities. As the mode of polymerization, batch process and continuous process can both be adopted. A slurry polymerization process or a solution polymerization process using an inert hydrocarbon solvent such as propane, butane, isobutane, pentane, hexane, heptane, octane and the like, a bulk polymerization process using propylene keeping liquid at the polymerization temperature as a medium, and a gas phase polymerization process can also be practiced.
At the time of main polymerization, a chain transfer agent such as hydrogen and the like may be added for the purpose of regulating molecular weight of the formed polymer.
The olefins which can be used in the main polymerization are those having 3 or more carbon atoms. Specific examples of the olefin include propylene, butene-l, pentene-1, hexene-l, 3-methyl-butene-l, 3-methyl-pentene-l, 4-methyl-pentene-l, octene-1, decene-1, dodecene-l, cyclohexene and the like. Of these olefins, propylene and butene-1 are preferable for use in homopolymerization, and mixed olefins consisting mainly of propylene or butene-1 are preferable for use in copolymerization. Of these olefin monomers, propylene is particularly preferred. In the copolymerization of the present invention, two or more kinds of olefin compounds selected from ethylene and the above-mentioned olefin compounds may be used in the form of a mixture. Compounds having a plurality of unsaturated bonds such as conjugated dienes and non-conjugated dienes can also be used in the copolymerization.
The first characteristic feature of the polypropylene used for production of the biaxially oriented film of the present invention consists in that it exhibits a good stretchability in the process of film-making. Further, the second characteristic feature thereof consists in that a biaxially oriented film obtained by biaxially stretching said polypropylene is excellent in transparency and stiffness.
The polypropylene produced according to the process of the present invention contains a specified quantity of 23xc2x0 C. decalin-soluble fraction. The content of 23xc2x0 C. decalin-soluble fraction in said polypropylene is in the range of from 3.0 to 10.0% by weight, preferably from 3.0 to 9.0% by weight and particularly preferably from 3.5 to 8.5% by weight. If the content of 23xc2x0 C. decalin-soluble fraction in said polypropylene exceeds the above-specified upper limit, the biaxially oriented film prepared therefrom is insufficient in stiffness. If the content of 23xc2x0 C. decalin-soluble fraction in said polypropylene is lower than the above-specified lower limit, the biaxially oriented film obtained therefrom is insufficient in stretchability.
The temperature at which the polypropylene of the present invention exhibits a complex elastic modulus of 1xc3x97109 dynes/cm2 when a vibration of 110 Hz is applied to the polypropylene is in the range of from 134 to 152xc2x0 C. and preferably from 137 to 149xc2x0 C. If said temperature is higher than the above-specified upper limit, stretchability is insufficient. If said temperature is lower than the above-specified lower limit, stiffness of the biaxially oriented film is insufficient.
Melt flow rate (MFR) of the polypropylene of the present invention at 230xc2x0 C. is in the range of from 0.5 to 10.0 g/10 minutes and preferably from 1.0 to 8.0 g/10 minutes. MFR is a parameter representing the average molecular weight of a polymer, and its greater value means a lower average molecular weight. If MFR of said polypropylene is higher than the above-specified upper limit, stretchability is not good. If MFR of the polypropylene is lower than the above-specified lower limit, flow property at the time of extrusion is not good to bring about undesirable results.
Into the polypropylene of the present invention, ethylene and xcex1-olefins having 4 or more carbon atoms may be copolymerized unless the object of the present invention is damaged by their copolymerization.
Into the polypropylene of the present invention, a stabilizer, a slipper, an antistatic agent, an anti-blocking agent and the like may be incorporated, unless the object of the present invention is damaged by adding these additives. A variety of inorganic and organic fillers may also be added, unless the object of the present invention is damaged by their addition.
The polypropylene of the present invention is made into a film and subjected to a stretching processing usually in the following manner to give a biaxially oriented film. Thus, the propylene is melted in an extruder, and thereafter extruded from a T die and cooled and solidified by means of cooling rolls to give a sheet-form material. Subsequently, the sheet thus obtained is pre-heated and stretched in the longitudinal direction by means of a number of heating rolls, and then laterally stretched by means of a heating oven consisting of a pre-heating part, a stretching part and a heat-treating part, after which it is subjected to a corona treatment if desired, and finally wound up. Although the melting temperature of the polypropylene varies depending on molecular weight, the above treatment is usually carried out at a temperature of from 230xc2x0 C. to 290xc2x0 C. The temperature of longitudinal stretching is from 130xc2x0 C. to 150xc2x0 C., and the draw ratio in the longitudinal direction is usually from 4 to 6. The temperature of lateral stretching is from 150xc2x0 C. to 165xc2x0 C., and the draw ratio in the lateral direction is usually from 8 to 10.
The biaxially oriented polypropylene film produced in the above-mentioned manner is superior to prior biaxially oriented films in transparency and stiffness, while retaining a good stretchability.